1. Field of Invention
This invention relates to organic electronic devices, and more specifically to, organic electronic devices having a single thin layer comprising three functionally optimized components uniformly dispersed therein.
2. Description of Related Art
A photoconductive layer for use in electrophotography may be a single layer or it may be a composite layer. One type of composite photoconductive layer used in xerography is illustrated in U.S. Pat. No. 4,265,990, incorporated by reference in its entirety herein, which describes a photosensitive member having at least two electrically operative layers (i.e., a dual layer photoreceptor structure). One layer comprises a photoconductive layer that is capable of photogenerating holes and injecting the photogenerated holes into a contiguous charge transport layer. Generally, where the two electrically operative layers are supported on a conductive layer, the photoconductive layer is sandwiched between the contiguous charge transport layer and the supporting conductive layer. In another embodiment, the charge transport layer is sandwiched between the supporting electrode and a photoconductive layer.
Photosensitive members, e.g., photoreceptors, having at least two electrically operative layers as described above, provide excellent images when charged with a uniform electrostatic charge, exposed to a light image and thereafter developed with finely developed electroscopic marking particles. A key component of modem photoreceptors is the charge generation layer (CGL) which absorbs imaging light and produces the conducting charge that is used to discharge the charge on the photoreceptor surface and hence form an electrostatic image. For reasons of electrical performance and cycling stability, it is desirable that such a charge generation layer be as thin as possible, yet absorb more than 90 percent of the light to which it is exposed. Thus, it is desirable to coat a charge generation layer to a thickness of about 0.1 micrometer to about 0.2 micrometer (100 nanometers to 200 nanometers) taking into account the binder polymer.
Organic electronic devices are typically dual layer structures having a junction formed between the two layers. Such a junction usually determines the responsiveness of the device and is dependent upon how well the contact between the two layers is controlled, the specific material composition, and the like. Production of these junctions often involves using vapor or vacuum deposition of the active species.
In order to increase the efficiency of organic electronic devices, it is desirable to have an interface or junction between the two layers to produce the smallest possible obstruction to free current flow, i.e., have the smallest possible resistance at the junction.
Ideally, the optoelectronic functionality would exist in a single layer without a junction as an additional variable. However, a single layer would have to be very thin, at least about 200 nm or less, in order to provide a sufficient field at desired low operating voltages in order to enable current flow.